1. Field of the Invention:
This invention relates to techniques for coupling signals from a rotating device, and more particularly to a method and apparatus for measuring nip pressure of a rotating roll, such as a press roll or a calender roll.
2. Description of the Prior Art
It is common practice in the papermaking industry to sense nip pressure by mounting a transducer within a roll and coupling pressure indicative signals generated by the transducer to an external measuring and indicating circuit. Heretofore this has entailed the use of slip ring assemblies which comprise slip rings and brushes. Inasmuch as this apparatus must be constantly operated, although nip pressure reading may not be constantly taken, slip ring assemblies must be precise and rugged, require a minimum of maintenance and have a long life. Also, inasmuch as strain gauges, thermocouples and the like are low signal devices, the signal to noise ratio is of importance and noise is generally kept at a low level through the use of special precious metal alloys. Accordingly, slip ring assemblies tend to be relatively expensive.
This expense may become compounded when it is necessary to couple signals from a number of separate rotating rolls, as may be the case in a large papermaking, press or printing facility.